1. Field of the Invention
The present invention relates to an organic light-emitting device provided with a plurality of organic light-emitting elements different from each other in emission color.
2. Description of the Related Art
Organic light-emitting elements (organic electroluminescence elements) have been actively researched and developed these days. An organic light-emitting element involves the following problems: the securement of a color purity and an improvement in luminous efficiency. One known solution to the problems is a micro cavity structure in which an electrode on a light extraction side is made semi-transparent so that light emitted from a light-emitting layer is resonated between both electrodes.
For example, International Patent Publication No. WO 01/039554 discloses a display device in which a light-emitting layer is interposed between a first electrode formed of a light reflection material and a second electrode formed of a transparent material; and at least one of the second electrode and the light-emitting layer has a resonating portion for resonating light emitted from the light-emitting layer. The device is formed so that an optical path L of the resonating portion has the positive minimum value satisfying the following Equation 2:(2L)/λ+Φ(2π)=m  Equation 2where m represents an integer; L represents the optical path of the resonating portion; Φ represents a phase shift produced upon reflection of light beams generated in the light-emitting layer on both ends of the resonating portion; and λ represents the peak wavelength of the spectrum of a light beam which is one desired to be extracted from the light beams generated in the light-emitting layer.
In addition, Japanese Patent Application Laid-Open No. 2004-127795 discloses that an optical path from a light emission center to each reflective layer is defined.
When semi-transparent layers (semi-transparent electrodes) formed in a plurality of organic light-emitting elements have the same thickness, the semi-transparent layers of the respective organic light-emitting elements are different from each other in transmittance and reflectance owing to the wavelength dispersibility of a material for each semi-transparent layer, so that the respective organic light-emitting elements are different from each other in intensity of resonance. Accordingly, an organic light-emitting element having a relatively low intensity of resonance involves a problem that the luminous efficiency of the element cannot be sufficiently improved. In addition, an organic light-emitting device has a serious problem of a chromaticity difference due to a view angle, and the more intense the resonance, the larger a view angle difference.